62Jeff

Worst case, check post 7 in this thread
http://forums.corvetteforum.com/c1-a...quick-fix.html

Kerouac

Okay. Thanks a lot. I'll let you know what happens. One last question: is it worth trying the 5amp replacement without worrying about the bulbs? Or is that just a waste of time?

62Jeff

It's worth the fuse first. Your car might not be pulling as much amperage as mine did

If you have a multimeter, remove the 4 amp fuse, turn the dash lamps on, connect the multimeter across the fuse holder terminals and see what amps are being pulled.

Kerouac

You are top-notch, 62Jeff. I'll get into this tomorrow and report back. Have a great night.

rich5962

Jeff, I remember your extensive work when you had your problem, and it makes sense that moving to the 5 Amp fuse was the solution. I'd imagine Chevrolet would have come out with a TSB to change that 4 to a 5 amp fuse for all 63 up cars with AC. I don't know if that ever happened. It should have.

But.....I'm wondering if there's a bit of corrosion or bad connection in the instrument light feed circuit somewhere too on the OP's car. If the fuse panel is original it could be a issue of loose rivets on the fuse clips, or on the backside loose or corroded terminals.

OP? Did they change the headlight switch as part of their work? The switch has the rheostat dimmer, so there's a potential connection flaw there too. Did they replace the bulbs? The replacements today are offshore "crap" IMO, and as we all know, the term "specifications" is not in the Asian suppliers vocabulary. Case in point....the repro '58-'62 headlight switches with their crap circuit breaker out of spec, turning headlights into blinkers.

I know that a car with AC has the extra 1893 bulb for the AC controls, requiring a tad more current for the dash lights, but it was working for many years with the 4 amp fuse in there. Now not so. All I'm saying is maybe something changed when the car was in the shop, now showing up at night as all of their test drives were during the day?

...just thinkin' maybe there's more to this than a few more milliamps of fuse, and there's some hidden corrosion/bad connection somewhere or parts changed affecting this too.

Curious, so I went through some numbers again....

Bulb qty/type data from the AMA specs:
Gauges 7 1816
Clock 2 1816
Radio 1 1893 (assuming OP has one and it was on)
Heater Ctls 1 1893
AC Ctls 1 1893

9 1816's (9 x 4W(@13V) = 36W) and 3 1893's (3 x 4.7W(@14V) = 14.1W) Total 50.1W

50.1W @ 12V = 4.175A
50.1W @ 12.5V = 4.008A
50.1W @ 13V = 3.85A
50.1W @ 13.5V = 3.71A
50.1W @ 14V = 3.57A

Note anything below 12.5 volts is critical, so the battery, VR, Alternator condition and all car electrical load conditions play a big role in that little dinky dash light circuit.

Unless you test each bulb at all voltages, the above numbers are average only. Why Sylvania's specs for both types are at 2 different voltages is confusing.

Sometimes it's hard to think that after weeks of work and thousands of dollars put into these 45-50 years olds that everything is fine. But there's always some little PITA problem that shows up after a restoration. Nature of the beast.

Rich

62Jeff

Actually, it has 2 bulbs, not 1, at 0.33 Amps each.

We don't know if that is true. The OP just bought the car, we don't know if the seller didn't drive it at night, or worse - knew of this issue and didn't tell the OP.


Also, note that in 65 they added 2 more 0.33 Amp bulbs to the main cluster, over what had been in play for 63/64, so a 65 A/C pulled 1.32 Amps more than a 63/64 without A/C.

I'm not going to rehash my nightmare, and can't speak to the root cause of the OP's issue.

Kerouac

Quick question, Jeff, if your on here: can I use a 6amp to replace the 4, or is that dangerous? Having some trouble finding a parts place with a 5amp.

62Jeff

When I was going through my drama, with a completely new harness, I was told by forum members that 6 Amps was safe for the wiring I had. My memory is that LectricLimited told me 5 amp was safe for my harness (and they were the makers of it) and that is what drove me to shoot for a circuit draw of under 5 amps.

I don't know how old or stressed your wiring is.

Maybe a better choice is to get a cheap multi-meter (you will use it elsewhere during your tenure as an old car owner) and see what kind of draw you are getting on that circuit?

Kerouac

I found some 5amps. I have a multimeter and was planning on checking the draw when I pull the blown 4amp. Do I need to disconnect the battery before putting the test leads on the clips in the fuse box? And does it matter which side gets the red and which side gets the black?

62Jeff

No, just remove the fuse and then clip each of the test leads to one of the metal tabs that hold the fuse, so the multi-meter is replacing the fuse.

No.

Connect the multi-meter, set it to measure Amps, pull the headlight switch to engage the dash lights, and then immediately look at the multi-meter to see what the draw is.

Remember that your multi-meter is replacing the panel lamp fuse, so that circuit is now only fused IF your multi-meter is internally fused. In other words if you see something like 8 or 9 amps on your multi-meter, turn off the lights immediately before you start cooking wiring.

Kerouac

Okay, with the multimeter attached and the car NOT running the draw was 3.8amps. I went ahead and put the 5amp in anyway, thinking that maybe when the car runs it surges above that (?). Panel lights now light. I'll take it for a drive and see what happens. That's usually when the fuse blows -- 5 minutes or less into a drive. I'll let you know what happens. Thanks very much, Jeff.

62Jeff

Ok, I forgot about that part - yes with my car running I had higher amps than at rest, although my car was over 4 at rest to begin with.

I recall that I could turn the lights on in my garage, and after about 5 minutes the fuse would blow. That was before I went to a 5 amp fuse and lower rated bulbs.

Kerouac

62Jeff: You are a genius, brother. Just took the car for a one hour drive at highway speed (and then some) with the panel lights on. Lights stayed on the whole time! Looks like the 5amp is going to do the trick (although I'll be keeping some 5amp fuses and a fuse puller in the glovebox from now on). I really appreciate you walking me through that whole thing. If I'm ever in your area I owe you a beverage of your choice. Very grateful, pal.

And to all of you others who weighed in, thanks to you as well. I really appreciate this Forum.

keri45

Why must you use the Studs? Will Dash NOT go back correctly otherwise?

62Jeff

Howdy,
By replacing the mounting screws with 1/4x20 studs several inches in length, you gain the ability to slide the cluster closer to the driver's seat, while allowing those studs to bear the weight of the cluster. Without the studs, the cluster would be a bit unwieldy to handle and put stress on the wires as it hung by the wires.

Once you are done, simply push the cluster back into position, remove a stud and install a mounting screw, remove another stud and install a mounting screw, etc.

Jeff

keri45

Thanks makes good sense...do you think I need the same or Diff Approach to ONLY Replace the Upper Headlight Warning Bulb? thanks

hope2

you guys are way more tech than me, changing all the bulbs is nuts, first of all there is most likely a short if this issue just popped up. I would guess light switch or pinched wire, especially if "just been in the shop for four weeks"

62Jeff

Depends on how flexible you are. Pull the seat and then get under the dash to see what you can access.

JohnZ

What you probably don't recognize yet is that the instrument cluster isn't plastic like most other cars - it's a solid zinc die-casting, and it's HEAVY.

tics67

I am following this thread an had a question. My dash lights ( which all work) do not illuminate the cluster very well at all. Do I change the bulbs and fuse as suggested or is there another way to jack it up a bit !. Thx